I want to remove one object from my render so that it leaves just a transparent background
I'm not a very advanced Blender user so take this for what it's worth... Could you not render the scene without the water (using Cycles, I assume) and then simply take that image and the &quot;pool&quot; from the LuxCore render and merge the two in Photoshop?
Theoretically, you could also remove the water from one image and replace with colour corrected water from the other image in P'shop, too.